What exact­ly is a ra­dio­pho­nic art? One that re­nounces the vi­sible? Not on­ly. To try to de­fine it, we need to go back over the his­to­ry of ra­dio and the sin­gu­lar paths ta­ken in the me­dium since the 1910s. This will bring to light a rich and com­plex set of r